Recently, the demand for small, sealed, rechargeable lead-acid batteries has increased dramatically. In contradistinction to the familiar automotive-type lead-acid batteries, these batteries are small, relatively lightweight, sealed and leakproof. As a consequence, they are capable of delivering a steady current in any position or orientation. Typically, these batteries are employed in emergency lighting systems, portable power and garden tools, engine starting systems and in standby electrical systems for computer applications.
Like all lead-acid batteries, however, these batteries are subject to off-gassing during recharging periods. During the recharge cycle, the water contained within the battery may be decomposed into hydrogen and oxygen. In order to provide long life for these batteries, it is necessary to promote oxygen recombination within each cell. It is known that a pressurized environment between 30-50 pounds per square inch (psi) within the cells will expedite oxygen recombination.
One of the problems facing the battery industry is the maintenance of a sound post seal. Most current designs employ epoxy to seal a lead electrode of post to a plastic battery cover. Unfortunately, it is very difficult to get a good sealing bond between the epoxy and the lead post during typical mass production techniques.
Moreover, over an extended period of time, the sulfuric acid electrolyte tends to creep up the post to the seal. The acid chemically attacks the post thereby resulting in a porous layer on the post. In time, the electrolyte advances up the length of the post and under the epoxy seal until an open direct path is provided to the outside of the cover. This debilitating corrosion action destroys the high pressure seal, thus ensuring electrolyte leakage and shortened battery life.
Clearly, a post seal design that is capable of maintaining a sound seal about a battery post is desirable